We wish to continue our immunochemical studies of pollen allergens causing hay fever and asthma in allergic man. We will develop new simple methodology for isolating highly purified allergens in high yield by immunoadsorbent chromatography. Ultra-pure allergens will be fractionated from these preparations utilizing advanced isoelectricfocusing techniques. The allergens to be studied will include those most rapidly eluted from ragweed pollen, which are likely to be of greatest importance in causing ragweed allergy. Particular emphasis will be placed on investigating the allergenic and antigenic determinants of Ra5, a ragweed allergen of relatively simple structure (mol. weight 5,200). We will also vigorously pursue the development of allergen derivatives known as "allergoids", defined as derivatives which have greatly reduced allergenic activity, but which have largely retained the ability to immunize protectively against the native allergen. Such preparations have great potential usefulness in improving the immunotherapy of allergic humans.